


count me unimpressed on the interspecies pregnancy bullshit

by avosettas



Category: Undertale (Video Game)
Genre: (sort of), Dusttale Sans (Undertale), Dusttale Sans/Horrortale Sans/Killer Sans/Reader, Horrortale Sans (Undertale), Killer Sans (Undertale) - Freeform, M/M, Mild Hurt/Comfort, Morning Sickness, Multi, Pregnancy, Reader is pregnant, Reader-Insert, Tooth-Rotting Fluff, Weird Biology
Language: English
Status: Completed
Published: 2021-01-17
Updated: 2021-01-17
Packaged: 2021-03-14 19:53:45
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,475
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28800885
Author URL: https://archiveofourown.org/users/avosettas/pseuds/avosettas
Summary: Each morning, you would wake up nauseated and weak from a lack of magic, and stumble your way to the bathroom.Today, you sit cross-legged in front of the toilet, practically still half-asleep, but too nauseous to be anywhere else. The smell of whatever cleaning products you’d used last time you cleaned didn’t help; they only make your stomach roil unpleasantly.
Comments: 2
Kudos: 49





	count me unimpressed on the interspecies pregnancy bullshit

**Author's Note:**

> for @Tyraxes1 on twitter! 
> 
> i kind of went "i will shove all my monster pregnancy headcanons in here... and then i'll die" lmao. anyway i love doing reader inserts with polyships it fucking SLAPS thank u goodnight
> 
> oh also background cream bc they wormed their way in there.

The child was Killer’s, of this you were sure. Nevermind that both Dust or Horror would be fathers to them as well - the soulling sitting inside you, feeding from your (limited, human) magic, was indeed biologically Killer’s, and you knew from how _sick_ you were. 

Your morning sickness had begun with you vomiting a mixture of some unknown black substance and the previous night’s dinner into the kitchen sink, with Horror holding your hair back and nervously murmuring something about lost nutrients.

Cross, hovering behind you, unsure of how to help, had been the one to suggest that that black substance looked an awful lot like what came from poor Killer’s eye sockets when he was emotional. He’d looked so guilty, like a kicked puppy, when Killer hid in his room for the rest of the day.

And so it continued: each morning, you would wake up nauseated and weak from a lack of magic, and stumble your way to the bathroom.

Today, you sit cross-legged in front of the toilet, practically still half-asleep, but too nauseous to be anywhere else. The smell of whatever cleaning products you’d used last time you cleaned didn’t help; they only make your stomach roil unpleasantly. 

“mornin’,” Dust suddenly rasps behind you, distracting you from your current predicament. His hands are warm against your forehead, fingers carding your hair back. “y’feelin’ alright?” 

Apparently, that’s the cue you need to get sick, suddenly launching yourself forwards towards your porcelain god. Dust steadies you with a hand on your back, the other still keeping your hair from getting dirty as you hack up the previous night’s dinner. He mumbles something behind you, quiet and encouraging, but you can’t really make it out. 

“c’mon, here…” A tissue is held to your nose, and you blow; it comes back dripping black when Dust pulls it away, and he winces and leans up to flush the toilet before you can look. “better out than in, i guess.” 

“I hate this,” you mumble in reply, leaning heavily onto him. You’re shivering now, but Dust’s grip is warm. “Like… damn, baby. Stop making things hard for me.” 

Dust laughs, close to your ear, and presses a hand to your stomach. “yeah, kiddo. stop making things hard for them.” With a sigh, he adds to you, “think killer’s upset about it, though.” 

“We knew an interspecies pregnancy would be hard,” you point out, curling closer to him. “Between his DT and LV, your LV and magic, and Horror’s magic, it was guaranteed to be tough no matter what.” 

(Nightmare had lectured you, when you’d asked him late one night, because you’d been afraid that if you had asked your mates they would think you were afraid. 

DT drew magic from its host, sometimes superseding their natural magic, though since Killer’s was naturally produced, there shouldn’t have been as much to worry about, theoretically. 

LV did the same, though it acted more like a faulty trampoline, constantly bumping the host’s magic upwards, and occasionally dragging it down _painfully_ , simply drawing from it endlessly as DT did. A child who had a parent with high LV wouldn’t be born with LV, of course, but their magic could be finicky, even painful to use.

And magic, of course, what monsters were made from. On one side of the spectrum was Dust, with his uncontrollable, reactive magic; on the other was Horror with his feeble, barely-there magic. Neither was ideal; children need magic to grow, and too much _or_ too little was detrimental.)

“yeah,” Dust agrees quietly, rubbing a thumb over your swollen stomach. “but he’s still upset about it. worried about you, mostly.” 

“Of course he is,” you reply with a good-natured roll of your eyes. “And so is everyone else, including the idiots here who aren’t even my mates!” 

Dust laughs at that, a soft wheezing noise that you’re quite fond of. He knows you aren’t wrong, though; Cross refused to let you go outside alone half the time, only acquiescing if his own mate distracted him, and it was obvious that both Dream and Nightmare were worrying from afar, too. Dream was constantly asking how you were doing, and every time you returned to your room, there were books of children’s fairy tales or books on monster pregnancies on the bedside table, obviously left by Nightmare. 

It was kind of cute, and, aside from Nightmare, it was also getting kind of annoying. 

“gotta keep an eye on ya,” Dust says fondly. 

“ _I_ gotta get off the bathroom floor,” you argue, though he easily lets you out of his grip when you squirm. “And I guess I should find Killer, too.” 

“should eat breakfast first,” he snorts. “‘r else you’ll have two anxious skeletons instead of one.” 

“You mean I’ll have three instead of two,” you retort, brushing your hand over Dust’s hood. He leans up into it with a soft purr, though he settles back onto the floor when your hand leaves him.

“yep,” he agrees. “go get ‘em, sweetheart.”

Food sounds like a _terrible_ idea to your brain, but your stomach rumbles as you make your way down to the kitchen. Not to mention that if you didn’t eat, Horror would worry, and there was nothing you hated more than worrying the castle’s resident teddy bear. 

Maybe some breakfast would do you good, anyway. Something light, like toast.

“Good morning,” you call as you enter the living room. Dream and Cross are on the couch, Dream still half asleep, and Cross looks only slightly more awake, probably on account of the coffee in his grip. They both wave clumsily at you, and you have to suppress a bit of a giggle at their sleepiness as you pass them. 

Horror has the kitchen to himself, and he purrs happily when you lean your head against his shoulder, the rough, deep noise soothing in your exhausted state. “mornin’, pumpkin.” 

“Morning,” you reply, moving slightly to look at what he’s doing. There’s a cookbook on the counter in front of him, opened to a recipe for some kind of stew, though there’s a pan with bacon cooking beside it on the stove. 

“makin’ dinner… ‘nd my breakfast,” he tells you in response to your curiosity, and then he shifts to reach the toaster. “got your breakfast… right here.” 

It’s just toast with butter, crispy but not burnt, and you grin. “Thanks.” 

Horror makes a rumbling sound, not quite a purr, and leans down to nuzzle your head a bit, before mumbling, “how‘re you… how’s the morning… uh, the morning thing?” He holds you by your hips, and it’s weird, feeling your stomach touch him but not the rest of you. 

(Before the pregnancy, you used to be able to slot yourself easily against him, head able to rest in the crook of his neck. Now you just feel like a balloon, and the worst part is you can’t cuddle any of your mates full on; it always has to be from the side, or with your back facing them now, never face-to-face.)

Your reply is slightly garbled by the crunching of the toast in your mouth as you chew, but you manage. “It sucks.” 

Horror hums a bit, hands moving from your hips to smooth over your stomach. His hands are warm, and you lean forward to rest your head on his chest, but you don’t quite make it that far. He doesn’t let you complain over it, though, instead leaning down to nuzzle you once more. 

“don’ like that you’re hurtin’ from this,” Horror mumbles quietly. “you’re so good through it, though… hardly complainin’, and lettin’ us take care of you…” 

He seems to remember the toast then, only half eaten. “I’m working on it, big guy,” you assure him, gripping his elbows gently. “Takes me a bit.” You reach for one of the pieces though; might as well get started, and stop him from worrying, too.

“...i’m glad you’re still… managin’ meals…” Horror murmurs against your hair, seemingly unwilling to let you go even as you try to finish your breakfast. He scrapes his lower jaw against the crown of your head slowly. “glad y’let me… take care a’ you,” he adds louder. 

“I don’t mind,” you reply softly, grinning despite yourself. “...Hey, speaking of taking care of someone, do you know if Killer’s been down here to eat yet?” 

“he was… gone when i woke up,” Horror says, perhaps a bit grumpily. “‘nd i wake up early.” 

“Hm.” You’re loath to leave Horror, warm and cuddly as he is, but he’s fine here. Not to mention that Killer will probably be just as cuddly once he cheers up. “I guess I should go find him.” 

“y’think he’s upset?” 

“Yeah,” you sigh. “I’m gonna grab him some juice and then smother him with kisses ‘til he _knows_ I’m not mad at him.” 

Horror chuckles, “i’ll join you when ‘m done here,” he promises, and then sends you on your way with a juicebox and some crackers. 

Finding Killer could be a hard task; aside from Nightmare, he probably knows the castle better than anyone else, on account of having been here the longest. For all you know, he could be in some secret nook or cranny that not even Nightmare knew of. 

It’s not that hard, though; when you knock on his bedroom door, he opens it without a fuss, cracking a wide, crooked grin at you. “hey, sweetheart. what’s up?” 

“You know what’s up,” you reply, trying to sound stern as you shoulder your way past him into the room. He barely sleeps in here anymore, since all three of your mates tend to join you in your room. It shows; the bed is completely unmade, with only a sheet and a bare pillow, and the air just _feels_ stale. 

Reading Killer is impossible on a good day, but you sit yourself on his bed with a huff and pat the space beside you. “C’mon, sit with me.” 

“takin’ control?” he asks. “i like it.” 

You roll your eyes. “I see right through the innuendos, mister. Come talk to me.” 

That shuts him right up. Killer slumps next to you almost meekly, and doesn’t say anything. It’s rare he’s at a loss for words, and it generally means he’s thinking too hard.

And he’s clearly distracted, so you lean over and press a kiss right outside the rim of his eye socket. “I know something’s eating you.” 

“...i shouldn’t have. um.” His face is rather red, and it’s usually a sight you appreciate; it’s so hard to fluster such a relentless flirt. But he’s clearly upset, so you don’t tease, just hold his hand loosely. He grips it tightly when he feels it, and you don’t complain, waiting for him to speak.

“i shouldn’t be a father,” he says finally. “i mean, i. biologically. that’s all.” 

“You know a lot of humans get sick when they’re pregnant, right?” you ask gently. “This isn’t some weird, interspecies, DT-fueled thing. It’s completely normal.” 

“it’s normally black? ‘nd i know it doesn’t usually last this long.” Killer replies, deadpan. When you don’t respond, he just snorts. “figured.” 

“Even then, it’s still not _different_ ,” you press. “I’d be getting sick if the baby were biologically Horror or Dust’s, too, wouldn’t I? And _I_ know that the nausea and stuff tends to last the entire pregnancy for monsters, instead of just the first three months like humans usually get.” 

“...it’s different,” he mumbles, not meeting your eyes. “if it were either of the other two, that’s just - it’s being weak, or feverish. not…” 

“And you’d blame them if -” Killer shuts you up before you can even finish with a glare. 

“‘course not,” he sighs after a moment, flopping onto his back. He’s still gripping your hand, so you fall with him, though you’re content to lay against his shoulder, and he throws an arm around you. “it’s just… i dunno, i guess i’m bein’ stupid,” he finishes with another sigh. 

“You are,” you assure him, pressing another kiss to his jawbone. “It’s okay, though. We always knew I was the smart one.” 

Killer snorts at that, “sure, okay.” 

Quieter, you tell him, “I love you,” but before he can respond, both of you startle at the bang on the door. Killer clutches you close and pulls a knife out of god-only-knows where, but after a moment, Dust barges in, followed by Horror shuffling in slower. 

“did you get him to stop being an idiot?” Dust asks you. Killer grumbles something, though it’s quickly muffled by Horror climbing onto the bed and cuddling up to Killer’s other side, partially on top of him despite his large size. 

“Hopefully,” you reply. You glance at the two behind you as Dust contemplates how to best join the cuddle pile; Horror is holding Killer’s mandible in one of his hands, shaking it back and forth a bit. 

“you’re a… dumbass,” he tells Killer. “‘nd y’need to eat somethin’.” 

“kinda busy being dogpiled,” Killer replies easily. “or, uh. mate-piled?” 

“i’m not on top of you,” Dust argues as his wraps his arms around you, having decided to basically use you as an oversized stuffed animal. Horror looks conflicted for a moment, before he decides that he feels left out since he’s not touching you, and he rests a hand on your belly to fix that issue. 

“two outta three ain’t so bad.” 

You tune the banter out easily, and if you were a monster, you’d certainly be purring contentedly. This is your favorite place in the entire multiverse; in the arms of your mates, knowing that they’re all happy, and you are, too - 

Suddenly, the wind gets knocked out of you, but it’s strange - like it’s from the inside of you’re body. It takes you a moment to realize, but then you squeal, “The baby kicked!” 

Horror is on you first, both hands pressed to your middle, and then Dust is shifting his hands down, too. Killer is last, because he has to squirm out from under Horror, but there’s plenty of room for - 

You all gasp this time - partially from pain, in your case, but you’re sure that they all felt it. Horror is nuzzling your belly, purring loudly, and Dust is mumbling something into the back of your head, so quietly that you can’t hear, though based on the tone you’re sure it’s something soft and loving. 

Killer is the most affected, still staring even after the baby stills, but his target soul is a bright, bright heart, nearly a normal monster soul. When he sees you looking, he ducks his skull to nuzzle into your shoulder instead, quietly responding to your earlier declaration, “love you too.” 

Yeah, definitely your favorite place in the multiverse. You wouldn’t trade it for anything, you’re sure of that.

**Author's Note:**

> twitter @avosettas (18+)


End file.
